1. Field of the Invention
The present invention relates to a chemical vapor deposition apparatus which includes a variable gas-flow adjusting unit which uniformly distributes reaction gas introduced into a reaction chamber.
2. Description of the Related Art
In general, CVD (Chemical Vapor Phase Deposition) is mainly used for growing various crystal films on various substrates.
Compared with LPE (Liquid Phase Epitaxy), the quality of crystal grown by CVD is excellent, but the growth speed of crystal is relatively low.
To overcome such a problem, a growth method is widely adopted, in which films are simultaneously grown on several substrates in one growth cycle.
However, when films are simultaneously grown on several substrates, the temperature of the respective substrates and a reaction gas flow on the substrates should be constantly maintained, in order to guarantee the same quality for the films grown on the respective substrates.
To achieve such a construction, a variety of methods have been used. In a first method, several injection pipes are used to constantly maintain gas flows on the substrates. In a second method, several substrates are arranged in a radial shape with respect to one rotation axis and are rotated on the same axis. In a third method, several substrates are rotated independently from each other. Such methods may be separately used or may be combined.
However, in the method in which several substrates are arranged on one rotation axis and reaction gas is introduced toward the center of the inside of a reaction chamber from the outside of the reaction chamber in a direction perpendicular to the rotation axis, the uniform flow of the reaction gas cannot be implemented. Accordingly, it is difficult to grow a high-quality thin film on a wafer.